Design method of two-dimensional chiral lattice structure applied to hollow blade

Abstract

The invention relates to the field of aero-engine structure design, in particular to a design method of a two-dimensional chiral lattice structure applied to a hollow blade. The design method comprises the following steps: establishing a parameterized model of a chiral lattice structure unit cell, wherein geometric parameters of the parameterized model at least comprise parameters for directly controlling the wall thickness of the structure; based on the parameterized model, a finite element analysis model capable of applying periodic boundary conditions is established and used for calculating the equivalent Poisson's ratio of the chiral lattice structure unit cells; and constructing a parameter optimization model based on a genetic algorithm, and solving to obtain the optimal geometric parameters of the chiral lattice structure unit cells. According to the method, the wall thickness is restrained through parametric modeling, the manufacturability of the structure is guaranteed, the chiral dot matrix with the preset negative Poisson's ratio is actively designed through optimization, the impact resistance is remarkably improved while light weight is achieved, and the method is suitable for filling and reinforcing design of parts such as aero-engine hollow blades.

Description

Technical Field

[0001] This invention relates to the field of aero-engine structural design, and in particular to a design method for a two-dimensional chiral lattice structure applied to hollow blades. Background Technology

[0002] In the development of aviation technology, with the continuous improvement of aero-engine performance, more stringent requirements have been placed on lightweight design and aerodynamic efficiency. To achieve lightweight goals, hollow blade structures, formed by partially removing internal materials from the blades, have gradually been applied and promoted. However, with the continuous increase in the hollowness of hollow blades, how to ensure that the blades have sufficient resistance to foreign object impacts during engine operation while meeting lightweight requirements has become a key technical problem that urgently needs to be solved in this field.

[0003] In recent years, the maturity of metal additive manufacturing technology has provided a new process approach for the integrated forming of complex structures. Against this backdrop, filling the cavities of impact-sensitive areas inside hollow blades with lattice structures possessing excellent mechanical properties has become a highly promising reinforcement solution. Among these, chiral lattice structures have attracted attention due to their unique deformation mechanism. Chiral lattice structures generally exhibit a negative Poisson's ratio effect, meaning that under compressive loads, the structure contracts laterally in the direction of the force, causing material to accumulate in the load-bearing area, resulting in an indentation drag phenomenon with increased local density. This characteristic gives negative Poisson's ratio structures significant advantages in energy absorption and impact resistance, making them particularly suitable for aerospace components with special impact protection requirements.

[0004] However, applying lattice structures to practical engineering still faces many challenges. On the one hand, the metal additive manufacturing process itself imposes limitations on the geometric characteristics of formable structures, such as minimum wall thickness and minimum feature size. Traditional topology-optimized lattice structure design methods, while achieving configurations with superior performance, often result in non-uniform bar cross-sections or wall thicknesses, or even thin-walled features below manufacturing limits, rendering the design unsuitable for direct manufacturing. If the topology optimization results are geometrically reconstructed later to meet process requirements, their mechanical properties will inevitably change, defeating the purpose of optimization. On the other hand, existing design methods typically focus on optimizing macroscopic mechanical properties (such as stiffness and strength) without systematically considering and precisely constraining specific deformation modes (such as negative Poisson's ratio) and manufacturability (such as uniform wall thickness).

[0005] Therefore, there is an urgent need for a new type of lattice structure optimization design method that can precisely control the geometric parameters of the lattice unit cell to ensure that it meets the process constraints of additive manufacturing. At the same time, it can actively design a lattice configuration with a predetermined equivalent Poisson's ratio through optimization, thereby giving the structure excellent impact resistance on the basis of lightweighting, so as to meet the stringent requirements of key components such as hollow blades of aero-engines for multi-functional integration of load-bearing and impact resistance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention aims to provide a design method for two-dimensional chiral lattice structures applied to hollow blades. This method, while meeting the precise geometric parameter constraints of additive manufacturing processes, achieves active design and precise control of the equivalent Poisson's ratio of the chiral lattice structure, thereby providing a filling structure solution for hollow aero-engine blades that combines lightweight design, high load-bearing capacity, and excellent impact resistance.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention proposes a design method for a two-dimensional chiral lattice structure applied to hollow blades, comprising the following steps:

[0009] S1. Establish a parameterized model of the chiral lattice structure unit cell, wherein the geometric parameters of the parameterized model include at least the parameters used to directly control the wall thickness of the structure.

[0010] S2. Based on the parameterized model, a finite element analysis model capable of applying periodic boundary conditions is established to calculate the equivalent Poisson's ratio of the unit cell of the chiral lattice structure.

[0011] S3. Using the geometric parameters of the parameterized model as design variables, and minimizing the deviation between the equivalent Poisson's ratio and the preset Poisson's ratio as the optimization objective, a parameter optimization model based on a genetic algorithm is constructed and solved to obtain the optimal geometric parameters of the chiral lattice structure unit cell.

[0012] Furthermore, the chiral lattice structure includes intersecting transverse and longitudinal curve splines, and the geometric parameters of the parameterized model include wall thickness, the x and y coordinates of the first control point on the transverse curve spline, and the x and y coordinates of the second control point on the longitudinal curve spline.

[0013] Furthermore, the design variables are the x and y coordinates of the first control point and the x and y coordinates of the second control point.

[0014] Furthermore, the periodic boundary conditions are applied as follows: the lower left corner node of the chiral lattice structure unit cell is fixed; the corresponding nodes of the left and right boundaries are constrained to have equal longitudinal displacement; the corresponding nodes of the upper and lower boundaries are constrained to have equal lateral displacement; and the lateral displacement of the left boundary node is constrained to be zero and the longitudinal displacement of the lower boundary node is constrained to be zero.

[0015] Furthermore, the method for calculating the equivalent Poisson's ratio is as follows: apply a compressive displacement load longitudinally to the chiral lattice structure unit cell to obtain the longitudinal compressive displacement of the chiral lattice structure unit cell; obtain the transverse contraction displacement caused by the longitudinal compressive displacement; and calculate the equivalent Poisson's ratio based on the longitudinal compressive displacement and the transverse contraction displacement.

[0016] Furthermore, the preset range of Poisson's ratio is [-1.0, -0.2].

[0017] Furthermore, the parameter optimization model also includes a constraint condition: the volume fraction of the chiral lattice structure unit cell does not exceed a preset upper limit.

[0018] Furthermore, the optimization process of the parameter optimization model includes:

[0019] S301. Initialization: Randomly generate multiple sets of values ​​for the design variables to form an initial population, where each set of design variable values ​​constitutes an individual.

[0020] S302, Fitness Calculation: For each individual in the current population, the finite element analysis model in step S2 is called to calculate its corresponding equivalent Poisson's ratio, and the fitness value of the individual is calculated according to the optimization objective.

[0021] S303, Population Renewal: A new generation of population is generated by performing genetic operations such as selection, crossover, and mutation on individuals in the current population;

[0022] S304, Iteration and Output: Repeat S302 and S303 until the preset convergence condition is met or the maximum number of iterations is reached. Output the geometric parameter value corresponding to the individual with the best fitness value in the final population as the optimal geometric parameter.

[0023] The present invention also proposes a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-described optimized design method.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) By explicitly constraining the wall thickness as the core parameter of the parametric model, the optimization process is always carried out within the manufacturable geometric space. The resulting optimal structure naturally has a uniform wall thickness and can be directly used for additive manufacturing without any subsequent geometric reconstruction that may cause performance loss. This fundamentally opens up the path from high-performance design to reliable manufacturing.

[0026] (2) This invention sets the equivalent Poisson's ratio as the optimization target and automatically optimizes the spline morphology within the unit cell using a genetic algorithm, thereby enabling the systematic design of chiral lattices with a predetermined negative Poisson's ratio. This allows engineers to proactively design the indentation drag effect strength of the structure under impact for specific impact scenarios, achieving on-demand performance customization. Comparative results show that, at the same level of lightweighting, the structure designed in this invention significantly outperforms traditional hexagonal or triangular truss lattices in key impact resistance indicators such as energy absorption.

[0027] (3) This invention forms a complete automated design framework through parametric modeling, periodic boundary finite element analysis, and genetic algorithm optimization. This framework is highly versatile and not limited to specific sizes or materials. By adjusting the objectives and constraints, it can be extended to various performance optimizations. The entire process is algorithm-driven, avoiding trial and error based on experience. It can efficiently and automatically find the optimal solution in a vast design space, providing an efficient and reliable design tool to meet the stringent requirements of hollow blades and other components of aero-engines for multi-functional integration such as load-bearing capacity and impact resistance. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the parameterized model of a chiral lattice structure unit cell in an embodiment of the present invention;

[0029] Figure 2 This is a flowchart of parameter optimization based on genetic algorithm in an embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of the chiral lattice structure optimized according to an embodiment of the present invention;

[0031] Figure 4 This is a schematic diagram of a traditional hexagonal lattice structure.

[0032] Figure 5 A schematic diagram of a traditional triangular truss lattice structure;

[0033] Figure 6 A comparison of stress-strain curves for three lattice structures;

[0034] Figure 7 A comparison of strain-specific energy absorption curves for three lattice structures. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example

[0037] This embodiment proposes a design method for a two-dimensional chiral lattice structure applied to hollow blades, including the following steps:

[0038] S1. Based on the cavity dimensions and geometry of the hollow blades of an aero-engine, the macroscopic dimensions of the chiral lattice structure unit cell are determined. In this embodiment, the chiral lattice structure unit cell includes intersecting transverse and longitudinal curve splines. In this embodiment, both the transverse and longitudinal curve splines are centrally symmetric splines, and both have two inflection points. The length W of the transverse curve spline is 8 mm, and the height H of the longitudinal curve spline is 4 mm. To accurately define the geometric features, a two-dimensional rectangular coordinate system is established: the lower left corner vertex of the unit cell rectangular outline is taken as the origin O (0, 0), the horizontal direction to the right is the positive X-axis, and the vertical direction upward is the positive Y-axis.

[0039] Build as Figure 1 The parameterized model of the chiral lattice structure unit cell shown includes geometric parameters such as wall thickness t and x-coordinate of the first control point A (right bend) on the transverse curve spline 101. A with the vertical coordinate y A And the x-coordinate of the second control point B (upper inflection point) on the longitudinal curve spline 102. B with the vertical coordinate y B The coordinates of the first control point A are used to define the key control point coordinates of the shape of the transverse curve spline 101, and the coordinates of the second control point B are used to define the key control point coordinates of the shape of the longitudinal curve spline 102.

[0040] S2. Based on the parametric model, a corresponding finite element analysis model is established in the commercial finite element software ANSYS. To accurately predict the macroscopic mechanical behavior of a chiral lattice structure unit cell in an infinite periodic array, periodic boundary conditions are applied to the finite element analysis model. The periodic boundary conditions are applied as follows:

[0041] S201. Fix the lower left corner node of the chiral lattice structure unit cell; fix the lower left corner node of the unit cell to eliminate rigid body displacement.

[0042] S202. For each pair of nodes on the left and right boundaries that have the same Y-coordinate, couple their displacements in the Y-direction to keep them equal.

[0043] S203. For each pair of nodes on the upper and lower boundaries that have the same X-direction coordinates, couple their displacements in the X-direction to keep them equal.

[0044] S204. Constrain all nodes on the left boundary to have zero displacement in the X direction and all nodes on the lower boundary to have zero displacement in the Y direction to fully define the boundary conditions.

[0045] A small compressive displacement load is applied to the unit cell in the Y direction (longitudinal direction). The following results can be obtained through finite element analysis:

[0046] Unit cell volume ratio Its value is the area S of solid material within a single cell. mat With the total area S of the unit cell cell The ratio of S mat It can be obtained directly from the mesh of the parametric model or finite element analysis model. .

[0047] Equivalent Poisson's ratio : Obtained through calculation. First, extract from Under the action, the average lateral displacement of the right boundary node of the unit cell relative to the left boundary Then, according to the formula The calculation is performed. This value is a core indicator for measuring the strength of the negative Poisson's ratio effect of a structure.

[0048] S3. Using the geometric parameters of the parametric model as design variables, and the equivalent Poisson's ratio... Compared with the preset Poisson ratio The goal is to minimize the deviation F. A parameter optimization model based on a genetic algorithm is constructed and solved to obtain the optimal geometric parameters of the unit cell of the chiral lattice structure. Specifically:

[0049] Optimization problem definition:

[0050] Design variable: Select the x-coordinate of the first control point A. A The ordinate of the first control point A is y A The x-coordinate of the second control point B B The ordinate of the second control point B is y. B As an optimization variable, t is set to 0.8 mm in this embodiment.

[0051] Constraints: The volume fraction ρ0 of the chiral lattice structure unit cell is set to not exceed a preset upper limit ρ. maxTo ensure a lightweight structure, in this embodiment, ρ max =0.3.

[0052] Optimization objective: The objective function is defined as follows:

[0053]

[0054] In this embodiment, The value range is set to [-1.0, -0.2]. If the preset Poisson ratio is too large (close to 0), the negative Poisson ratio effect will be weak, and the improvement of impact resistance will be limited. If the preset Poisson ratio is too small (less than -1.0), it may cause excessive distortion of the spline, resulting in local stress concentration or manufacturing difficulties, which will damage the overall performance.

[0055] The optimization process of the parameter optimization model includes:

[0056] S301. Initialization: Randomly generate multiple individuals to form an initial population. Each individual is composed of a set of x. A y A x B y B composition;

[0057] S302 Fitness Calculation: For each individual in the current population, substitute it into the parameterized model in S1 to automatically generate the corresponding geometric configuration. Call the finite element analysis in S2 to calculate the equivalent Poisson's ratio of the geometric configuration under periodic boundary conditions, and calculate the fitness value of the individual according to the objective function. The smaller F is, the higher the fitness.

[0058] S303, Population Update: Based on the fitness obtained in S302, high-quality individuals are selected to enter the mating pool using roulette wheel selection or tournament selection. A single-point crossover operation is performed on the paired individuals in the mating pool with a first preset probability, exchanging some variable values ​​to generate new individuals. A random small perturbation is applied to the new individuals with a second preset probability to form a new population. In this step, the random small perturbation of the new individuals with the second preset probability is performed to maintain population diversity and avoid premature convergence. In this embodiment, the first preset probability is 0.8, and the second preset probability is 0.05.

[0059] S304, Iteration and Output: Repeat S302 and S303 for the new population until the preset convergence condition is met or the maximum number of iterations is reached. Output the t and x values ​​corresponding to the individual with the best fitness in the final population. A y A x B y B As the optimal geometric parameter output, in this embodiment, the final output x is... A = (6.635004), y A= (2.990435), x B =(3.528312)y B = (2.806362). (The coordinates of the upper left control point of the longitudinal spline are (-4.71688, 8.06362), and the coordinates of the upper right control point of the transverse spline are (13.17502, 9.90435).

[0060] To better illustrate the beneficial effects of the present invention, see references. Figure 2 This invention establishes an impact simulation model of a lattice structure in the software ANSYS. Using this model, the impact resistance performance of the chiral lattice structure optimized in this embodiment, the traditional hexagonal lattice structure, and the triangular truss lattice structure are compared. Figure 3 A schematic diagram of a chiral lattice structure is shown. Figure 4 A schematic diagram of a hexagonal lattice structure is shown. Figure 5 A schematic diagram of a triangular truss lattice structure is shown. The hexagonal lattice structure, triangular truss lattice structure, and chiral lattice structure have the same volume ratio. The lattice structure is composed of lattice structure unit cells arranged in both the transverse and longitudinal directions. The impact simulation model, from bottom to top, consists of a lower plate 201, a lattice structure 202, and an upper plate 203. Both the lower plate 201 and the upper plate 203 are rigid bodies; the lower plate 201 is fixed, and the upper plate 203 is subjected to an impact load at a constant velocity. Based on the reaction force between the upper plate 203 and the lattice structure 202, the following... Figure 6 The stress-strain curve shown; calculations based on the stress-strain curve yielded the following results. Figure 7 The strain-specific energy absorption curve shown is from... Figure 6 and Figure 7 It can be seen that the chiral lattice structure optimized by the method of the present invention exhibits better energy absorption capacity under impact load due to its controllable and strong negative Poisson's ratio effect, which significantly improves the hollow blade's resistance to foreign object impact.

[0061] The specific embodiments of the present invention are provided to enable those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0062] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A design method for a two-dimensional chiral lattice structure applied to hollow blades, characterized in that, Includes the following steps: S1. Establish a parameterized model of the chiral lattice structure unit cell, wherein the geometric parameters of the parameterized model include at least the parameters used to directly control the wall thickness of the structure. S2. Based on the parameterized model, a finite element analysis model capable of applying periodic boundary conditions is established to calculate the equivalent Poisson's ratio of the unit cell of the chiral lattice structure. S3. Using the geometric parameters of the parameterized model as design variables, and minimizing the deviation between the equivalent Poisson's ratio and the preset Poisson's ratio as the optimization objective, construct a parameter optimization model based on a genetic algorithm and solve it to obtain the optimal geometric parameters of the chiral lattice structure unit cell.

2. The design method for a two-dimensional chiral lattice structure applied to hollow blades according to claim 1, characterized in that, The chiral lattice structure unit cell includes intersecting transverse and longitudinal curve splines, and the geometric parameters of the parameterized model include wall thickness, the x and y coordinates of the first control point on the transverse curve spline, and the x and y coordinates of the second control point on the longitudinal curve spline.

3. The design method for a two-dimensional chiral lattice structure applied to hollow blades according to claim 2, characterized in that, The design variables are the x and y coordinates of the first control point and the x and y coordinates of the second control point.

4. The design method for a two-dimensional chiral lattice structure applied to hollow blades according to claim 1, characterized in that, The periodic boundary conditions are applied as follows: the lower left corner node of the chiral lattice structure unit cell is fixed; the corresponding nodes of the left and right boundaries are constrained to have equal longitudinal displacement; the corresponding nodes of the upper and lower boundaries are constrained to have equal lateral displacement; and the lateral displacement of the left boundary node is constrained to be zero and the longitudinal displacement of the lower boundary node is constrained to be zero.

5. The design method for a two-dimensional chiral lattice structure applied to hollow blades according to claim 4, characterized in that, The method for calculating the equivalent Poisson's ratio is as follows: apply a compressive displacement load in the longitudinal direction of the chiral lattice structure unit cell to obtain the longitudinal compressive displacement of the chiral lattice structure unit cell; obtain the transverse contraction displacement caused by the longitudinal compressive displacement; and calculate the equivalent Poisson's ratio based on the longitudinal compressive displacement and the transverse contraction displacement.

6. The design method for a two-dimensional chiral lattice structure applied to hollow blades according to claim 1, characterized in that, The preset Poisson ratio range is [-1.0, -0.2].

7. The design method for a two-dimensional chiral lattice structure applied to hollow blades according to claim 1, characterized in that, The parameter optimization model also includes a constraint condition: the volume fraction of the chiral lattice structure unit cell does not exceed a preset upper limit.

8. The design method for a two-dimensional chiral lattice structure applied to hollow blades according to claim 1, characterized in that, The optimization process of the parameter optimization model includes: S301. Initialization: Randomly generate multiple sets of values ​​for the design variables to form an initial population, where each set of design variable values ​​constitutes an individual. S302, Fitness Calculation: For each individual in the current population, the finite element analysis model in step S2 is called to calculate its corresponding equivalent Poisson's ratio, and the fitness value of the individual is calculated according to the optimization objective. S303, Population Renewal: A new generation of population is generated by performing genetic operations such as selection, crossover, and mutation on individuals in the current population; S304, Iteration and Output: Repeat S302 and S303 until the preset convergence condition is met or the maximum number of iterations is reached. Output the geometric parameter value corresponding to the individual with the best fitness value in the final population as the optimal geometric parameter.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the optimization design method as described in any one of claims 1 to 8.

Images